Routinely, the cells are placed in compression or else bonded on the periphery of their surface. A first display device is known according to document U.S. Pat. No. 6,606,132-B2 compressing an LCD screen between sheets of glass having resonance frequencies and thermal expansion coefficients similar to those of the LCD.
A second device is revealed in document CN 2,616,924-Y. It shows a frame clamping the optical stack based on a fastening system.
A third solution, shown in FIG. 1, is the use of adjustable spacers 12 and 15 and the installation of silicone seals 14 which serve as a damper for the periphery of the glass. This solution comprises structural parts 17 and inserts 18 pressing the various layers of the optical stack together. These structural parts are assembled mechanically by the fastening screws 16. This device ensures a precise slope on the glass stack and makes it possible to precisely adjust the pressure exerted on the thickness of the various sheets of glass. Depending on the batches of glass supplied, the thickness of the sheets may vary and the various spacers offer the possibility of precisely adjusting the assembly. Conversely, this solution requires having a considerable set of spacers in order to respond to the variety of thicknesses of glass. This constraint therefore has an impact on the cost of the solution. Moreover, adjusting the set of spacers and the pressure precisely greatly increases the time for assembling the solution.
A final solution consists of a pressure-setting element making it possible to control the force on the LCD cell and ensure the rate of compression on the damping seals. The pressure is exerted by an external cylinder and is maintained by transverse screws. The main disadvantage of this solution is that it requires costly production means for the pressure-setting relative to the assembly time.
These solutions have the disadvantage of being voluminous and costly. Added to this is the impossibility of developing around them a method of mass production. Today the new requirements make it necessary to propose a product having good performance in terms of withstanding thermal, electromagnetic, vibratory and impact stresses while not requiring manufacturing resources that are too complex or too costly.